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  • Title: Intramolecular control of protein stability, subnuclear compartmentalization, and coactivator function of peroxisome proliferator-activated receptor gamma coactivator 1alpha.
    Author: Sano M, Tokudome S, Shimizu N, Yoshikawa N, Ogawa C, Shirakawa K, Endo J, Katayama T, Yuasa S, Ieda M, Makino S, Hattori F, Tanaka H, Fukuda K.
    Journal: J Biol Chem; 2007 Aug 31; 282(35):25970-80. PubMed ID: 17620342.
    Abstract:
    Peroxisome proliferator-activated receptor gamma coactivator (PGC)-1 is a critical transcriptional regulator of energy metabolism. Here we found that PGC-1alpha is a short lived and aggregation-prone protein. PGC-1alpha localized throughout the nucleoplasm and was rapidly destroyed via the ubiquitin-proteasome pathway. Upon proteasome inhibition, PGC-1alpha formed insoluble polyubiquitinated aggregates. Ubiquitination of PGC-1alpha depended on the integrity of the C terminus-containing arginine-serine-rich domains and an RNA recognition motif. Interestingly, ectopically expressed C-terminal fragment of PGC-1alpha was autonomously ubiquitinated and aggregated with promyelocytic leukemia protein. Cooperation of the N-terminal region containing two PEST-like motifs was required for prevention of aggregation and targeting of the polyubiquitinated PGC-1alpha for degradation. This region thereby negatively controlled the aggregation properties of the C-terminal region to regulate protein turnover and intranuclear compartmentalization of PGC-1alpha. Exogenous expression of the PGC-1alpha C-terminal fragment interfered with degradation of full-length PGC-1alpha and enhanced its coactivation properties. We concluded that PGC-1alpha function is critically regulated at multiple steps via intramolecular cooperation among several distinct structural domains of the protein.
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